Effect of grain size of the precursor powder on the plastic deformation and the current carrying capacity of Bi-2212 wires

Abstract In the past two years, the record of current carrying capacity of Bi2Sr2CaCu2Ox (Bi-2212) wire has been broken many times by using improved powder, which shows that the precursor powder plays an important role in the preparation of Bi-2212 wire. In order to improve the quality of Bi-2212 precursor powder, this paper explored the effect of the grain size of the precursor powder on the uniformity of the plastic deformation of the wire, the grain alignment of the superconducting cores and the current carrying capacity of the wire. It was found that the plate-like large-grain precursor powder had the obvious bridging effect, which effectively prevented the Ag sheath of single-core wires from expanding freely inward, so that the single-core Bi-2212 wires with smooth Ag/oxide interface could be obtained. In addition, the precursor powder with the large plate-like grain size also had excellent slippage performance, resulting in the improving of the plastic deformation properties of multi-core wires. It could reduce the core breakage rate of multi-core Bi-2212 wire, and further improved the smoothness of Ag/oxide interface and the grain alignment of Bi-2212 cores. Under the combined action of the above two aspects, multi-core Bi-2212 wire with the uniform cores, orderly superconducting grains and low core breakage rate were prepared by large-grain precursor powder. The current carrying capacity of the final Bi-2212 wire was increased by more than 15%.